Sealed window for x-ray generator with shield for seal



7 R. M. GAGER 3,334,256

SEALED WINDOW FOR X-BAY GENERATOR WITH SHIELD FOR SEAL Filed March 20, 1964 2 Sheets-Sheet 1 ROBE/77M. 6465/? B I/Vl EIVTOR BUG/(HORN, BL ORE, KLA/POU/ST 8 SPAR/(MAN .47'70RNEYS R. M. GAGER Aug. 1, W67

SEALED WINDOW FOR X-RAY GENERATOR WITH SHIELD FOR SEAL 2 Sheets-$heet Filed March- 20, 1964 ROBERT M 6465/? IIVVENTOI? BUC/(HOP/V, BLORE, KLAROU/ST 5 SPAR/(MAN ATTORNEYS United States Patent Office 3,334,256 Patented 1, 1967 3,334,256 SEALED WINDOW FOR X-RAY GENERATOR WITH SHIELD FOR SEAL Robert M. Gager, Elmhurst, Ill., assignor to Dunlee Corporation, Bellwood, 11]., a corporation of Illinois Filed Mar. 20, 1964, Ser. No. 353,435 3 Claims. (Cl. 313-59) The present invention relates to X-ray generators and more particularly to an arrangement for protecting the mounting of a window in the -wall of the generator envelope to facilitate the emission of X-rays.

In X-ray generators having a glass envelope the X-ray emission window may comprise -a thin diaphragm of beryllium or other metal of low atomic number suitably sealed across the end of a tubular mounting member which in turn is sealed to the envelope by a glass-to-metal seal about an opening in the envelope wall. This glassto-metal seal is subject to bombardment by stray electrons primarily from the cathode, as a result of which a charge frequently builds up on the seal overstressing the glass envelope in the vicinity of the seal and breakdown of the glass frequently occurs.

It is, therefore, a particular object of the present invention to provide a means for shielding the glass-tometal seal of such a mounting from bombardment by electrons.

Another object ofthe invention is to provide a simple inexpensive shield for the glass-to-metal seal of a window mount.

Still other objects and advantages of the invention will become more apparent hereinafter.

In accordance with an illustrated embodiment of the invention an X-ray generator having a glass envelope is provided with an opening in the wall thereof for the emission of X-rays generated at the anode. Sealed to the envelope about such opening by a glass-to-metal seal is an outwardly projecting tubular metal member, across the end of which is sealed a diaphragm of an X-ray transparent metal such as beryllium. The beryllium diaphragm is mounted in a metal ring sealed to the end of the tubular member. Mounted on the ring and extending coaxially of the tubular member is a tubular metal shield which extends inwardly of the envelope and is provided with an outwardly extending peripheral flange whereby the shield intercepts electrons projected from the cathode toward the glass-to-metal seal thus protecting the seal and preventing the developmnt of an electrical charge thereupon.

For a more detailed description of the invention reference is made to the accompanying drawing wherein:

FIG. 1 illustrates in section a portion of a stationary anode type X-ray generator embodying the invention;

FIG. 2 is an enlarged view of a portion of the generator shown in FIG. 1;

FIG. 3 is a fragmentary sectional view of a rotating anode type X-ray generator incorporating the invention; and

FIG. 4 is a fragmentary sectional view taken along line 4 4 of FIG. 3.

Referring first to FIGS. 1 and 2, the illustrated X-ray generator comprises an envelope formed of glass having a cathode 12- mounted in one end. thereof and an anode 14 in the opposite end thereof. The cathode 12 is provided with a filament 16 for generating and focusing a beam 18 of electrons upon a target 20 of wolfram or other suitable material mounted in the face of the copper body of the anode 14. To facilitate the emission of a useful beam of X-rays, indicated at 21, from the envelope 10, an X-ray emission windows is provided in the wall thereof. Such window comprises a tubular mounting member 24 sealed to the periphery of an opening in such wall by a glass-to-metal seal 26. A ring or flange member 28 is brazed to the outer end of the member 24. A clamping ring 30 is adapted to be clamped against the flange member 28 by screws 29 so as to secure across the opening of the flange member a foil 32 of beryllium or the like. Preferably a gasket 34 of indium or like soft metal is positioned between the foil 32 and flange 28 to assist in the formation of a vacuum tight seal. A silicone grease of low volatility may be positioned about the periphery of the foil 32 and gasket 34 as indicated at 36 to assist in the formation of a vacuum tight seal as more particularly described in Zed J. Atlee Patent No. 2,730,637. An O-ring gasket 38 is also positioned between the flange 28 and member 30 near the periphery thereof to prevent the entrance of foreign matter into the gap therebetween.

To protect the glass-to-metal seal 26 a shield 40 is provided comprising a tubular portion 42 mounted on the flange 28 coaxially of the mounting member 24. The tubular portion is provided with longitudinal slits 44 defining fingers 46 having outwardly extending lips 48 on the ends thereof. The lips 48 are engaged beneath a peripherally extending projection 50 formed by a groove on the inner surface of the flange 28. As will be apparent the fingers 46 are flexed laterally to engage or disengage the lips 48 from the projection 50. The inner end of the shield 40 is'formed with an outwardly extending flange 52 which extends over the glass-to-metal seal 26 so as to intercept any stray electrons emerging from the cathode 12 and any secondary electrons from the target 20 so as to prevent such electrons striking the seal.

Referring now to FIG. 3, indicated at 50 is the envelope, which may be of glass or other suitable material, of a rotating anode type X-ray generator including a cathode 52 suitably mounted in one end of the envelope and an anode 54 suitably mounted in the opposite end and comprising a disc-like target member 56 of wolfram or other suitable material supported from a rotor 58. The cathode 52 is provided with a filament 60 for generating and focusing a beam of electrons upon the target member 56.

To facilitate the emission of an useful beam 62 of X-rays a window is provided in the envelope 50. Such window comprises a tubular metal member 64 sealed by a glass-to-metal seal 66 to the envelope about the periphery of an opening in the envelope wall. A metal ring 68 is secured as by brazing to the outer end of the metal member 64. A diaphragm 70 of beryllium or other relatively X-ray transparent metal is sealed to the ring 68 so as to define with the envelope 50 a vacuum tight enclosure.

In accordance with the invention a tubular metal shield 74 is mounted on the ring coaxially of the mounting member 64. The inner surface of the ring 68 is provided with an annular groove to receive outwardly extending lips 78 formed on the end of the shield. The shield 34 is also formed with a plurality of slits 80 extending longitudinally from the end formed with the lips 78 about half the length of the shield whereby the portions of the shield defined by the slits may be flexed laterally to permit insertion of the lips 78 into the aforementioned concentrically of the target 56 and envelope 50 so as to maintain maximum spacing of the shield between the anode, the cathode and the envelope. In the axial direction of the window the flange is circular. It has been been found that the presence of the shield effectively protects the seal 66 and prevents creation of an electrical charge in the area of the glass-to-metal seal, thus preventing breakdown of the seal.

Having illustrated and described a preferred embodi ment of my invention, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the spirit and scope of the appended claims.

I claim: Y

1. An X-ray generator comprising an anode and a cathode mounted within said envelope,

a tubular glass envelope having an opening in the side thereof for the emission of Xrays generated at said anode,

a tubular metal member sealed to said envelope by a glass-to-metal seal about said opening and extending outwardly from said envelope,

a metal ring sealed to the outer end of said member,

a diaphragm of a relatively X-ray transparent metal sealed to said ring across the opening thereof,

and a tubular metal shield mounted on said ring coaxially of said member and extending from said ring into said envelope, said shield having an outwardly extending peripheral flange on the end thereof within said envelope extending over said glass-to-metal seal.

2. An X-ray generator comprising an anode and a cathode,

is j

a tubular glass envelope enclosing said anode and cathode and having an opening in the side thereof for the emission of X-rays,

a tubular metal member sealed to said envelope by a glass-to-metal seal about said opening and extending outwardly from said envelope,

a metal ring sealed to the outer end of said member,

a diaphragm of a relatively X-ray transparent metal sealed to said ring across the opening thereof,

and a tubular metal shield mounted on said ring coaxially of said member and extending from said ring into said envelope, said shield having an outwardly extending peripheral flange on the end thereof within said envelope extending over said glass-to-metal seal, 4

' the opposite end of said shield having outwardly extending lips thereon and said ring having a groove therein receiving said lips,

said shield having a plurality of slits therein extending longitudinally from said opposite end whereby the end portions of said shield defined by said slits may be flexed laterally to insert said lips into said grooves.

3. An X-ray generator as set forth in claim 1 wherein said flange is curved concentrically of the axis of said envelope.

' References Cited UNITED STATES PATENTS 2,256,229 9/ 1941 Atlee et al 3l3-5 9 FOREIGN PATENTS 561,771 5/ 1944 Great Britain.

DAVID J. GALVIN, Primary Examiner. 

1. AN X-RAY GENERATOR COMPRISING AN ANODE AND A CATHODE MOUNTED WITHIN SAID ENVELOPE, A TUBULAR GLASS ENVELOPE HAVING AN OPENING IN THE SIDE THEREOF FOR THE EMISSION OF X-RAYS GENERATED AT SAID ANODE, A TUBULAR METAL MEMBER SEALED TO SAID ENVELOPE BY A GLASS-TO-METAL SEAL ABOUT SAID OPENING AND EXTENDING OUTWARDLY FROM SAID ENVELOPE, A METAL RING SEALED TO THE OUTER END OF SAID MEMBER, A DIAPHRAGM OF A RELATIVELY X-RAY TRANSPARENT METAL SEALED TO SAID RING ACROSS THE OPENING THEREOF, 